1. Field of the Invention
The present invention relates to hearing test equipment designed for musicians, recording studio engineers, audio professionals, and everyone else who desires to obtain for themselves accurate information about their hearing at their own recording facility or at home, using computer equipment and headphones.
2. Description of Related Art
Professional and home recording equipment that is based on digital technologies has significant flexibility. As of 1999, most commercial recording studios have integrated computer-based music recording and/or editing capabilities. These facilities are often staffed by engineers who have worked with sound at high volume for many decades, and so have some degree of hearing impairment (due to aging and to noise exposure) that they are not aware of because they do not, as a rule, get their hearing tested. Therefore, it is desirable to integrate hearing test procedures and equipment smoothly into these professional environments to allow these seasoned professional engineers to obtain accurate, confidential information about their hearing by using the computer in their facility. In contrast to conventional Audiometry, which is concerned with the frequency range of speech (125-8,000 hz), the use of computer equipment allows for self tests over the full range of audible frequencies present in music (20-20,000 hz). Since audio engineers use their own hearing in their profession as the reference standard, a hearing test can act as a xe2x80x9creference checkxe2x80x9d similar to a guitar tuning measurement device or a sound level measurement device.
In addition to large commercial recording facilities, every year hundreds of thousands of new, personal, home-based recording facilities are built that use Personal Computers as the primary recording and editing device. The numbers of such xe2x80x9cproject studiosxe2x80x9d is increasing so rapidly primarily because the cost of purchasing Professional Audio recording equipment has decreased dramatically. Digital technology has now placed Professional Audio recording equipment in the hands of the general musician population. Yet very few of these semi-pro equipment buyers have a good understanding of their own hearing. They therefore may work at a disadvantage, sometimes making adjustments to their equipment without realizing why. There is a need for these users of digital recording equipment to gain the same level of understanding about their hearing as the professionals.
Those familiar with the art know that stand-alone compact disks (CDs) with test tones are not accurate for all headphones, due to the wide range of variation in frequency response of headphones. Similary, it has been impractical in the prior art to establish a calibration reference at for example 1 khz, for each and every set of headphones, and then ensure that the signal levels at all other frequencies are also known. This is due for example to differences in coupler behavior and response, coupling pressure, and resonance peaks and dips that may exist. Without accurate tone generation either calibration or audiological test results that follow cannot be accurate.
Finally, the standard xe2x80x9cForced Responsexe2x80x9d method of audiological testing, where the actual level of each test frequency is varied by automation or by the Audiologist, is quite time consuming. It is desirable therefor to allow testing wherein the user directly controls the output level of each test frequency, which is a great deal faster and therefore easier to incorporate into engineers"" busy schedulesxe2x80x94and hence more likely to be used. Well established research from Bekesy onward has shown the Method of Adjustment to be faster, with greater test-retest reliability, than the Forced Response method. See the chapter, xe2x80x9cPyschoacoustics,xe2x80x9d by Arnold M. Small, in the book xe2x80x9cNormal Aspects of Speech, Hearing, and Language,xe2x80x9d Edited by Minifie, Hixon, and Williams, 1973: New Jersey, Prentice-Hall, Inc that describes the Bekesy method in some detail as it compares to other audiometric test procedures.
The present invention provides a hearing analyzer method and apparatus, and a user-operated, user-calibrated audiological test system which comprises software, a calibrator, and specified headphones. The frequency response of the headphones is measured. The soundcard of a computer is used to generate audiological test signals, and either the actual output level of those signals or the analysis of results is compensated by software to the frequency response of the headphones. The calibrator allows an accurate calibration level to be established for the soundcard output. The software provides for using the method of adjustment test procedure to perform several audiological tests.
In one embodiment, the invention provides a method for performing a hearing test using a system including a computer producing audio signals, headphones and volume control for the audio signals. The headphones are characterized by a data set including drive voltages for corresponding test frequencies at which a constant sound pressure level (SPL) is generated by the headphones. Further, the headphones are characterized by a calibrated drive voltage at a particular reference frequency which produces a particular sound pressure level output by the headphones. The method comprises coupling audio signals from the computer to the input of a calibration device which translates an input audio signal to output drive voltages. In addition, the output of the calibration device is coupled to the headphones. The output of the system is set to particular frequency, such as 1 kHz. The volume control for the audio signals at the particular frequency is adjusted until the calibration device produces the calibrated drive voltage on its output. With the volume control set for the system at the adjusted level, the user is prompted through a hearing test in the test frequencies, while the output of the system is controlled according to a data set characterizing headphones. In various embodiments, the user is prompted using a graphical user interface. For one example, the graphical user interface includes a graphical input construct appearing like a set of sliders for a set of frequencies. Software is used to control the computer to output tones according to frequencies in the set of frequencies in response to adjustment by the user of an indicator on the graphical input construct for each of the tones. The graphical user interface further includes resources for displaying results of the test, such as in the form of a graphical audiogram.
In one embodiment, the hearing test comprises a minimum audibility test. In yet another embodiment, the hearing test comprises an equal loudness test.
The calibrator according to one embodiment includes indicator light on the device which indicates when the calibrator is producing the calibrated drive voltage. The step of adjusting includes adjusting the volume control until the indicator light is illuminated. In one embodiment, first, second and third indicator lights are provided on the calibrator. The first indicator light indicates that the output of a calibration device is below the calibrated drive voltage. The second indicator light indicates that the output of the calibration device is about equal to the calibrated drive voltage. The third indicator light on the calibration device indicates that the output of the calibration device is above the calibrated drive voltage.
In yet another embodiment of invention, an apparatus is provided for conducting hearing tests. The apparatus includes a calibration device as described above, and computer software stored or provided to the computer in a machine readable medium, such as memory the computer, or a medium which is readable by the computer.
In one embodiment, the invention is a user-operated, user-calibrated, computer-based system that generates and administers full range (20-20,000 hz) audiometric testing after accurately establishing a reference calibration level.
Other aspects and advantages of the invention can be seen upon review the figures, the detailed description and the claims which follow.